The present invention relates to a novel process for the crystallization of lactitol, to a particulate crystalline lactitol product having novel properties, to the use thereof as in foodstuffs, pharmaceuticals and oral hygiene products, and to a special sweetener. The present invention specifically provides a crystalline lactitol product, wherein the crystals are produced by microcrystallization of lactitol from a liquid solution of lactitol.
Lactitol is a sweetener which can be used as a total or partial replacement for sucrose, however, its energy content is only about half of that of sucrose, and it does not cause increased blood glucose content; furthermore, it is non-cariogenic and hence tooth-friendly. Lactitol also can be used as an active ingredient and an excipient in pharmaceutical preparations, e.g. as a laxative.
The preparation of lactitol from lactose has been known for a long time. Industrially, lactitol is prepared from lactose by hydrogenation in the presence of a Raney nickel catalyst. The preparation is described e.g. in Wolfrom, M. L., et al., J. Am. Chem. Soc. 60, (1938) p. 571-573.
Crystalline lactitol is reported to occur in the anhydrous form as well as in the form of a monohydrate and dihydrate. Lactitol also crystallizes as a trihydrate. There seem to exist more than one distinct crystalline form of anhydrous lactitol.
Crystalline lactitol monohydrate as well as the di- and trihydrate and anhydrous lactitol may be used as sweetening agents resembling sugar. For instance, crystalline lactitol monohydrate may be used in dietetic products, confectionery, bakery products, cereals, desserts, jams, beverages, chocolate, chewing gums and ice-cream. The lactitol crystals may also be used in the production of oral hygiene products such as tooth pastes, and in the manufacture of pharmaceuticals.
Anhydrous lactitol may be crystallized from an aqueous solution as described in WO 92/16542. incorporated herein by reference. Anhydrous lactitol has a melting range of 149-152xc2x0 C.
Lactitol hydrate powders dehydrated to a moisture content of less than 3% have been prepared by drying both lactitol solution and crystalline hydrate. The hygroscopicity of these powders is utilized in drying moist mixtures (European Patent Application 0231643).
Crystallization of lactitol from aqueous solutions and the crystal structures of lactitol have been reported, among others, in van Velthuijsen, J. A., J. Agric. Food Chem. 27, (1979) p. 680; European Patent 0 039 981; J. Kivikoski et al. Carbohydrate Research, 233 (1992) 53-59; EP Patent Application 0 381 483; EP Patent 0456636; JP Patent Application 13220/89. The disclosures of said publications are incorporated herein by reference.
The crystallization of lactitol from a liquid such as from an aqueous or ethanolic solution requires specific crystallization conditions and fairly long crystallization times. Due to the nature of prior art suspension crystallization methods, all of the lactitol in the solution generally cannot be obtained in crystalline form. A part of the lactitol will always remain in the mother liquor and will be discarded with the mother liquor even after repeated series of crystallizations.
Lactitol can also be produced in solid form by granulation as described in background art PCT/FI97/00548. Spray drying of lactitol has also been attempted according to JP open-laid Patent Hei 2-255694 but the tests made were accompanied by many problems. Co-spray drying of a polyol composition containing mainly mannitol and up to 10% lactitol is described in WO 97/39739.
Thus, there exists a need for improving the production of solid lactitol and the present invention aims at satisfying that need.
The object of the present invention is thus, to provide a solid particulate crystalline lactitol product.
Another object of the present invention is to provide crystalline lactiol in a process which transforms a lactitol liquid into a solid lactitol product in one single overall operation.
An object of the invention is also to provide a novel particulate lactitol product which is suitable for use in the food industry as well as in the pharmaceutical and oral hygiene product industry.
A further object of the present invention is to provide a directly compressible lactitol product.
An object is also to provide novel edible, pharmaceutical and oral hygiene products containing lactitol.
Consequently, the present invention, as defined in the appended claims, provides a novel process for producing crystalline lactitol. Said process comprises contacting a liquid containing dissolved lactitol with gas suspended solid particles containing solid lactitol; causing substantial removal of the solvent component of said liquid and allowing the resulting lactitol material to form a composition of matter comprising a multitude of microcrystals of lactitol; and causing said lactitol composition to be conditioned during a further drying step to provide a product consisting essentially throughout its entire structure of a multitude of microcrystals of lactitol agglomerated together in a random manner.
In a preferred embodiment of the invention an aqueous solution of lactitol is got into contact with fluidized particles of microcrystalline lactitol, the wetted particles are dried in a flow of warm gas, and the lactitol on the surface of the particles is allowed to form new microcrystals.
By further conditioning the particles, the microcrystallization is allowed to proceed for a sufficient time to provide a final product consisting essentially of microcrystalline lactitol.
In a preferred embodiment of the invention the wetted particles are substantially dried while falling down with a co-current air stream and allowed to settle into a porous layer of agglomerated microcrystallizing lactitol, which is then conditioned and cooled. The microcrystallization conditions are selected so that the cooled layer is porous and brittle. If desired, the layer may be broken up into smaller fractions. Only a mild crushing action is needed to break up the agglomerated mass of microcrystals. The agglomerated product will primarily be broken up at the interfaces between individual crystals rather than by disrupting the crystals themselves.
In another embodiment of the invention the particles are retained in a gas suspended state in an air stream while additional liquid is sprayed onto their surfaces until the particles have grown to a predetermined size or weight. The particles are then removed from the air stream, e.g. by gravity and conditioned as described above.
The gas suspended microcrystalline lactitol particles are preferably provided by recirculating a portion of the microcrystalline lactitol produced in the process itself. Said particles may comprise dust entrained in circulating drying air or it may be dust or fine particles provided by the crushing of the agglomerated mass. At start-up milled crystalline lactitol may be used as solid feed to be replaced by microcrystalline lactitol when available.
The terms xe2x80x9cmicrocrystallinexe2x80x9d and xe2x80x9crnicrocrystalxe2x80x9d as used throughout the present specification and claims should be understood to mean very small crystals having a size which on an average is below 50xcexc, and generally is of the order of about 5-10xcexc, on an average. In contrast to the present microcrystals, the lactitol crystals obtainable by prior known crystallization techniques are discrete crystals which, on an average, are of the order of about 100-1000xcexc or larger.
Consequently, the present invention provides a novel particulate crystalline lactitol product wherein each particle substantially throughout its entire structure consists of a multitude of microcrystals of lactitol agglomerated together in a random manner.
Although the size of the lactitol particles according to the present invention is not critical and may vary according to the intended use of the product, the mean particle size of the lactitol product is generally below 10 mm, typically between about 0.1 and 2.0 mm. The preferred mean particle size is generally about 0.15-0.4 mm. The particle size and distribution may be control-led to sure intended use.
The microcrystals may be used as said discrete particles, they may be compressed and tabletted or they may even be given the form of ordinary sugar lumps or cubes.
The individual lactitol microcrystals generally comprise anhydrous lactitol and/or lactitol monohydrate. The crystal mass may also include other lactitol hydrate forms, such as lactitol dihydrate and/or amorphous lactitol. It is, however, for many applications preferred that the major crystalline form is anhydrous or monohydrate. In a preferred embodiment of the invention, the microcrystals consist essentially of anhydrous lactitol.
The microcrystalline lactitol product according to the present invention may be used as a bulk sweetener for the total or partial replacement of sucrose or other sweetening agents. Thus, it is useful in dietetic products, confectionery, bakery products, cereals, desserts, jams, beverages, chocolate, chewing gums and ice creams. It is also useful in pharmaceuticals such as laxatives and in oral hygiene products such as tooth pastes.
The microcrystalline lactitol product according to the present invention is particularly useful for tabletting purposes due to its agglomerated crystal structure, and partly also because of the presence of different physical forms of particles. The product may, for instance, be used as a tabletting excipient in the same way as lactose.
A further embodiment of the present invention relates to a special sweetener which comprises microcrystalline lactitol. Such a sweetener may include other components such as excipients and/or other sweeteners.
Such other sweeteners are preferably also non-cariogenic sweeteners such as intense sweeteners taken from the group comprising dipeptide sweeteners, saccharin, acesulfame K, stevioside, cyclamate, sucralose and neohesperidin dihydrochalcone. However, the preferred non-cariogenic sweetener consists essentially of the microcrystalline lactitol according to the invention.
The excipients which may be used in the sweetener and/or other applications such as in pharmaceutical preparations may comprise, for instance, microcrystalline cellulose, carboxymethyl cellulose, polydextrose, dextrose, maltodextrin, lactose, sugar, etc. as well as other sugar alcohols. The microcrystalline lactitol according to the present invention may also be used in preparations as a substantially inert component such as a diluent, carrier and/or excipient.
The microcrystalline lactitol of the present invention is preferably produced in a pure lactitol form, i.e. containing throughout essentially only lactitol. Although the lactitol may be mixed with other compounds, lactitol should always form the major portion of the composition and preferably the product should contain over 80%, preferably more than 90% and most preferably more than 98% lactitol.
If the solid and/or liquid feed comprises other components, such as one or more of the above mentioned excipients, or other active ingredients, the product discharged from the microcrystallization apparatus will contain said other component(s) as an integral part of its structure. A secondary spray of another solid or liquid component may also be fed into the microcrystallization apparatus into contact with the microcrystallizing lactitol. Said other compounds should be selected so as to not interfere adversely with the microcrystallization of the lactitol.
Further embodiments of the present invention relate to products made from the novel microcrystalline lactitol. Such products are typically edible products, pharmaceutical products and/or oral hygiene products such as those mentioned above. Special advantages are obtained, for instance, in the production of chocolate from the microcrystalline lactitol of the present invention.
A further embodiment of the invention relates to a directly compressible crystalline lactitol product comprising the novel microcrystalline lactitol and to tablets produced by compressing a composition containing such microcrystalline lactitol.
The present invention will now be described in greater detail. This description should, however, not be taken as limiting the invention to the precise wording thereof. A person skilled in the art will be able to provide numerous modifications and variations of the process without deviating from the invention as defined in the appended claims.